The present invention relates to photography.
In particular, the present invention relates to exposure meters which may be independent or built into a camera.
The present invention relates especially to an electrical system which forms such an exposure meter and which is compensated so as to avoid the influence of fluctuations in ambient temperature and power source voltage, so that the electrical system of the invention can always provide correct results in a stable manner.
As is well known, certain advantages flow from utilizing semiconductor elements for systems of this type. Thus, the use of semiconductor elements enables such systems to have a compact, light-weight construction and to be operated advantageously by utilizing a battery as a power source. However, semiconductor elements have proved not to be ideal devices under all circumstances inasmuch as they are easily influenced by fluctuations in ambient temperature and the manner in which they operate varies with variations in power source voltage. As a result to these latter semiconductor properties it is extremely difficult to provide accurately operating electrical circuits which utilize semi-conductors. In the case of a photographic exposure meter, whether of the built-in type or an independent unit, it is required that operations take place over a wide range of ambient temperature, which include high temperature resulting from direct sunlight during the summer to extremely low temperature encountered in mid-winter in the mountains, for example. Thus it is required that structures of this type be capable of operating properly over a temperature variation of from approximately + 50.degree.C to - 30.degree.C. In addition, since such exposure meters are usually operated with a battery the power of which is consumed during operation, the voltage supplied by the battery varies considerably, thus introducing a further fluctuating factor which can undesirably influence the accuracy of the operation. Accordingly, unless compensation is made for fluctuations in temperature and variation in power source, it is not possible to provide an electrical system of the above type which is capable of providing the information required for optimum exposure of film.